kernel: Store "next" pointer before notifying B_EVENT_INVALID.

Once B_EVENT_INVALID has been set, the select routine is free to
delete the select_info at any time. We therefore cannot access
the "next" pointer after notify_select_events returns.

May fix a KDL seen by trungnt2910.

src/system/kernel/events/wait_for_objects.cpp

@@ -745,8 +745,9 @@ notify_select_events_list(select_info* list, uint16 events)
 {
 	struct select_info* info = list;
 	while (info != NULL) {
+		select_info* next = info->next;
 		notify_select_events(info, events);
-		info = info->next;
+		info = next;
 	}
 }
 

src/system/kernel/fs/fd.cpp

@@ -556,8 +556,9 @@ deselect_select_infos(file_descriptor* descriptor, select_info* infos,
 			}
 		}
 
+		select_info* next = info->next;
 		notify_select_events(info, B_EVENT_INVALID);
-		info = info->next;
+		info = next;
 
 		if (putSyncObjects)
 			put_select_sync(sync);

src/system/kernel/thread.cpp

@@ -2242,9 +2242,10 @@ thread_exit(void)
 	while (info != NULL) {
 		select_sync* sync = info->sync;
 
+		select_info* next = info->next;
 		notify_select_events(info, B_EVENT_INVALID);
-		info = info->next;
 		put_select_sync(sync);
+		info = next;
 	}
 
 	// notify listeners